Apparatus for selectively removing material from an article

ABSTRACT

Material is removed from opposite sides of a substrate while protecting intermediate surfaces thereof by employing a pair of wheels biased toward each other to establish peripherial contact. Each of the wheels has a urethane tire bonded thereto and is mounted for rotation in opposite directions to one another. The substrate is engaged between the urethane tires to mask the intermediate surfaces and as the wheels are rotated the substrate is displaced relative to streams of air abrasive particles eminating from each one of a pair of nozzles mounted on either side of the wheels. Material from the opposite sides is removed by the abrasive action of the air abrasive particles while the intermediate sides thereof are protected against the abrasive action by the urethane tires masking the intermediate surfaces.

[451 Aug, 7, 1197s APPARATUS FOR SELECTIVELY REMOVING MATERIAL FROM AN ARTICLE [75] Inventors: Arthur James Matthews, Jr., High Point; Raymond Otis Terry, Jun, Winston-Salem, both of NC.

[73] Assignee: Western Electric Company,

Incorporated, New York, N.Y.

[22] Filed: Dec. 17, 19711 [21] Appl. No.: 209,088

[52] .8, CI. 51/8, 51/310 [51] Int. Cl. B24c 3/112 [58] Field of Search 51/8, 9, 11, 14, 51/16, 310, 215 HM, 1l0-l14, 137-139 [56] References Cited UNITED STATES PATENTS 2,118,832 5/1938 Wean et al 51/9 3,133,379 S/l964 Green et a1. 51/8 FOREIGN PATENTS OR APPLICATIONS 870,970 3/1953 Germany 51/14 OTHER PUBLICATIONS McI-Iale, D. T., Grinding of Ferrite Cores, in Western Electric Digest No. 10: p. 5-6, Apr. 1968.

Primary Examiner-Donald G. Kelly Assistant jixqmiperl-Ioward Goldhe rg Attorney-W. M. KaimWTL. Williamson et a1 57 ABSTRACT Material is removed from opposite sides of a substrate while protecting intermediate surfaces thereof by employing a pair of wheels biased toward each other to establish peripherial contact. Each of the wheels has a urethane tire bonded thereto and is mounted for rotation in opposite directions to one another. The substrate is engaged between the urethane tires to mask the intennediate surfaces and as the wheels are rotated the substrate is displaced relative to streams of air abrasive particles eminating from each one of a pair of nozzles mounted on either side of the wheels. Material from the opposite sides is removed by the abrasive action of the air abrasive particles while the intermediate sides thereof are protected against the abrasive action by the urethane tires masking the intermediate surfaces.

3 Claims, 3 Drawing Figures APPARATUS FOR SELECTIVELY REMOVING MATERIAL FROM AN ARTICLE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to an apparatus for selectively removing material from an article and more particularly to an apparatus for removing unwanted resistor material from opposite sides of a substrate while masking intermediate sides.

2. Description of the Technical Problem In the manufacture of thin film resistors, a resistor material such as nickel-chromium alloys, cermets, tantalum .or tantalum nitride is deposited either by sputtering or evaporation onto a surface of a non conductive substrate, e.g., a ceramic or glass substrate. There are two embodiments of substrates used in thin film resistor manufacture. One embodiment has a flat surface onto which is deposited a resistor film. The other embodiment, which is the one most commonly used, has grooves embossed on a surface onto which is deposited a resistor film; these grooves are more or less V-shaped in cross section and run along a surface of the substrate to form a track. During the evaporation or sputtering of the resistor film onto a desired surface of the substrate, e.g., the surface having the grooves embossed therein, the resistor material deposited covers all of the surface exposed as well as some of the side surfaces. As can be appreciated, the deposited resistor material on the top surface adheres tenaciously to the substrate whereas the resistor material that randomly deposits on the side surfaces of the substrate does not always tenaciously adhere thereto. In addition to the difference in adherence between the resistor material deposited on the top surface and the side surfaces, the amount of resistor material deposited on the top surface can be more accurately controlled than the amount of resistor material randomly deposited on the side surfaces.

Prior to the trimming of the resistor material to a predetermined resistance value it is desirous to either open the conductive path created by the resistor material randomly deposited on the sides of the substrate or remove it completely. In the instance where the resistor material is deposited on a flat substrate, one way of trimming is to remove resistor material by scratching with a stylus. To reduce the amount of scratching required to trim the resistor to value it is necessary that the amount of resistor material deposited on the substrate be controlled to tight tolerances. As stated previously, during the deposition of resistor material on the desired surface of a substrate the material is also randomly deposited on the sides thereby establishing a conductive path between the resistor material on the desired surface and on that deposited on the sides. Because the amount of resistor material deposited on the sides is random it must be removed completely so that the resistor path consists only of the resistor material deposited on the top'surface which can be controlled.

The prior art method of removing .the unwanted resistor material from the side surfaces of the substrate provides for passing a grinding wheel over the side surfaces to remove the unwanted resistor material deposited thereon. This method of removing the resistor material from the side surfaces of the substrate is errpensive and inefficient. It is expensive because precision equipment must be used and inefficient because the equipment must be continuously maintained in precise working order to consistently remove a predetermined thickness of material from the sides of the substrate. As can be appreciated, grinding the side surface of the substrate also removes part of the resistor material covering the top surface because reducing the width of the substrate also reduces the width of the resistor material deposited on the top surface. If too much resistor material from the top surface is removed, the resistor can not be subsequently trimmed to value because excessive removal of resistor material increases the resistor value of the resistor film beyond a predetermined range and the value can not be lowered unless resistor material is deposited on the preexisting film. If less than a calculated amount of resistor material is removed, excessive scratching to trim the resistor to value must be made. Even if the equipment operates properly, the grinding of the side surfaces may weaken the bond between the resistor material and the substrate causing the resistor film to flake off.

As previously stated the more common practice to make thin film resistors is to deposit a thin film onto a ceramic substrate with grooves embossed in it to form a resistor track. This type of resistor is trimmed by grinding the top of the substrate, thereby effectively re ducing the width of the grooves and the amount of resistive material therein until the resistance is trimmed to value. Removing the resistor material by grinding breaks the continuity between the resistor material on the top surface and the side surface thereby establishing a shunt resistive path on each side. The prior art practice is to open these shunt resistive paths by cutting a notch in the sides of the substrate. The necessity of obviating the resistor material from the side surfaces which establishes the shunt current paths can be appreciated when it is realized that the resistor material on the side surfaces may not'have the resistive characteris tics or adherence desired. Further, having the random deposited resistor material on the side surface may cause abnormal resistance value changes during the use of the thin film resistor due to unstable characteristics of the side film.

At the present time the shunt current path established by the resistor material deposited on the side surfaces is opened by using a cutting wheel to cut a notch in the side of the substrate transverse to the current path. This method of opening the shunt current paths is expensive and inefficient. It is expensive because the equipment must be continuously maintained in precise working order to assure that a notch cut into each of the side surfaces of the substrate does not extend into the resistor track. Even if the equipment operates properly it has been found that cutting a notch in both sides of a substrate mechanically weakens the substrate making it susceptable to cracking during handling.

SUMMARY OF THE INVENTION The invention contemplates an apparatus for removing material from a selected side of an article without removing material from two sides of the article directly adjacent the selected side by engaging the two sides of the article by a pair of resilient members to mask the two sides and displacing the selected side relative to a stream of abrasive particles to remove material therefrom while continuing to mask the adjacent sides.

DESCRIPTION OF THE DRAWING FIG.I is a perspective view of a substrate having a groove embossed in a surface after removal from a sputtering or evaporating chamber.

FIG. 2 is a perspective view having cut-away sections illustrating an apparatus for removing unwanted resistor material from the sides of the substrate of FIG. 1.

FIG. 3 is a partial view having a cut away section illustrating substrates of FIG. 1 as they move from a feeder into engagement with wheels of the apparatus of FIG. 2.

DETAILED DESCRIPTION Shown in FIG. 1 is a non-conductive substrate, e.g. a ceramic or glass substrate,.,generally shown as numeral 11 after removal from a sputtering or evaporating chamber (not shown). The substrate 11 has a predetermined groove configuration embossed in top surface 12 to form a resistor track 13. As can be appreciated, during the evaporation or sputtering of a resistor material 14 such as nickel-chromium alloys, cermets, tantalum or tantalum nitride onto the surface 12 and the resistor track 13 of the substrate 11, the resistor material 14 is also deposited on sides 16 (one of which is shown). As previously discussed the resistor material 14 deposited on the sides 16 of the substrate 11 are notched to permit proper trimming of a thin film resistor and prevent subsequent changes in resistor value. Although the substrate 11 has the resistor track 13 on the surface 12, it will become obvious that a substrate having a resistor track on opposite surfaces thereof or a substrate having a resistor material deposited on a flat surface may also be cleaned using the method and apparatus of this invention.

Referring to FIG. 2 there is shown a cleaning apparatus 21 which illustrates a preferred embodiment of this invention.

The apparatus 21 has a base 22, a gear compartment 23 defined by panels 24 and 26 and a cleaning compartment 27 defined by the panels 26 and 28. The panels 24, 26, and 28 are securely mounted at the bottom end as viewed in FIG. 2 in any conventional manner to the base 22. To further support the panels 24, 26, and 28 and to prevent pollution of the working area, the apparatus 21 is enclosed by a back panel 29 and a top panel 31 extending from the panel 24 to the panel 28, and a front panel 32 extending from the panel 24 to the panel 26. In each instance, the panels are interconnected in any conventional manner as by way of screws 3333. The front end of the cleaning compartment 27 as reviewed in FIG. 2 has a door 34 mounted between the panels 26 and 28. The door 34 has the right side as viewed in FIG. 2 mounted in any conventional manner to one section of a spring hinge 36 and the other half of the spring hinge 36 is mounted to the left end of the front panel 32 as viewed in FIG. 2 in any conventional manner. The spring hinge 36 is biased to maintain the door 34 in the closed position, thereby providing easy access to the cleaning compartment while isolating the cleaning compartment from the working area. If observation of the cleaning operation is desired the door 34 and the panel 28 may be made of any well knonw rigid transparent material.

Referring now to the gear compartment 23, a drive shaft 41 having a gear wheel 42 securely mounted near the left end as viewed in FIG. 2 is mounted at the left end in a bearing 43 mounted in the panel 26, and has a portion of the right end as viewed in FIG. 2 passing through and supported by bearing 44 mounted in the panel 24. The right end of the drive shaft 41 is connected to a motor 46 mounted on the base 22 for rotating the drive shaft 41 in a clockwise direction as viewed in FIG. 2. A boss member 47 has a pair of parallel generally rectangular plates 48 and 49 securely mounted on either side of a T-shaped member 51. A bearing is mounted in each of the upper ends of the plates 48 and 49 in spaced alignment to form a pair of upper bearings 52-52 of the boss member 47 as viewed in FIG. 2. Similarly a bearing is mounted in each of the bottom ends of the plates 48 and 49 in spaced alignment to form a pair of lower bearings 53 (one of which is shown) of the boss member 47 as viewed in FIG. 2. The drive shaft 41 supports the boss member 47 for pivotal movement by way of the pair of lower bearings 53 of the boss member 47 which are mounted on the drive shaft 41. In this manner, when the drive shaft 41 is rotated in a clockwise direction by the motor 46 as viewed in FIG. 2, the drive shaft 41 and the gear wheel 42 rotate but the boss member 47 remains at its position or is free to pivot about the drive shaft 41.

Referring now to the T-shaped member 51 of the boss member 47 there is shown a headed bolt 56 which passes through a hole 57 in the leg of the T-shaped member 51 and is screwed in a hole 58 formed in sloping side 59 of a trapazoidal member 60 which is mounted to the base 22 by way of screws 61--6l. A spring 62 is mounted on the shaft of the bolt 56 between the head and the leg of the T-shaped member 51 to bias the boss member 47 to the left about the drive shaft 41 as viewed in FIG. 2. The amount of movement of the boss member 47 to the left under the action of the spring 62 is limited by screw 63 which is screwed through the leg of the T-shaped member 51 and rests on the surface of the sloping side 59 of the trapezoidal member 60.

A shaft 66 having its right end as viewed in FIG. 2 supported by the upper pair of bearings 52 of the boss member 47 has the left end passing through a slot 67 formed in the panel 26 into the cleaning compartment 27. A gear wheel 68 is mounted on the shaft 66 such that the gear teeth of the gear wheel 68 mesh with the gear teeth of the gear wheel 42. In this manner, the rotation of the drive shaft 41 and the gear wheel 42 in a clockwise direction rotates the gear wheel 68 and the shaft 66 in a counterclockwise direction as viewed in FIG. 2. The slot 67 in the panel 26 permits movement of the shaft 66 and the gear wheel 68 to the left or right as viewed in FIG. 2, when the boss member 47 pivots about the drive shaft 41 under the bias or against the bias respectively of the spring 62. In this regard, as the gear wheel 68 is moved to the left or right, the gear teeth of the gear wheel 68 walk in the gear teeth of the gear wheel 42 thereby providing positive contact between the gear teeth at all times.

A second shaft 71 in spaced alignment to the first shaft 66 has the right end supported in a bearing 72 mounted in panel 24 and the right portion of the shaft 71 passing through bearing 73 mounted in panel 26 into the cleaning compartment 27 as viewed in FIG. 2. A gear wheel 74 is securely mounted on the shaft 71 such that the gear teeth of the gear wheel 74 mesh with gear teeth of an idler gear wheel 76. The idler gear wheel '76 is mounted on a bearing (not shown) which is mounted on a stud shaft 75 that passes through the panel 26 and held in position by way of bolt 77. The gear teeth of the idler gear wheel 76 mesh with the gear teeth of the gear wheel 42 securely mounted on the drive shaft 81. By providing this gear arrangement, the rotation of the drive shaft 411 and the gear wheel 412 mounted thereon in a clockwise direction by motor 86 rotates the shaft 66 by way of the gear wheel 68 in a counterclockwise direction while simultaneously rotating the idler gear wheel 76 in a counterclockwise direction which in turn rotates the gear wheel 78 to rotate the shaft 71 in a clockwise direction as viewed in FIG. 2. In this manner, the shafts 66 and 71 are rotated in opposite directions.

Referring now to the cleaning compartment 27, a pair of wheels generally shown as 78-79 each having a tire 81 and 82 made of a resilient material, such as we thane, bonded to a rim 83 and 88 respectively, are securely mounted on the shafts 66 and 71 by way of a hub 86 and 87 respectively. The tires 81 and 82 are selectively made of a resilient material because resilient material is more resistant to attack by air abrasive particles and being resilient it conforms to the surface of the substrate in contact therewith to mask the same. As will be appreciated, the width of the tires 81 and 82 corresponds to the width of the surface 12 of the substrate 11 (see FIG. 1) and the combined diameter of the tire and rim is such that when the shaft 66 is biased to the left as viewed in FIG. 2 by the boss member 417 the tires 81 and 82 are in surface contact with one another. Critical dimensions of diameter are not required as the movement of the boss member 47 which moves the shaft 66 and associated wheel 78 to the left as viewed in FIG. 2 under the biased action of the spring 62 can be adjusted by the limit screw 63. The limit screw 63 can also be adjusted to compensate for wear of the tires 81 and 82 through use by rotating the limit screw 63 to reduce the distance between the T-shaped member 51 and the sloping surface 59 of the trapazoidal member 68 thereby allowing the boss member 87 to pivot further to the left about the drive shaft 41 moving the shaft 66 and the wheel 78 further to the left as viewed in FIG. 2.

Mounted on each side of the wheels 78 and 79 is an air abrasive nozzle 91 and 92 such as those sold by S.S. White Company which are held by straps 93 and 98 to brackets 96 and 97 respectively. The brackets 96 and 97 are mounted to the underside of the top plate 31, as viewed in FIG. 2 in any conventional manner. The air abrasive nozzles 91 and 92 are positioned on the brackets 96 and 97 respectively such that a stream of abrasive particles eminating from each of the nozzles is directed to the contact area of the tires 81 and 82. Each of the nozzles 91 and 92 are connected to one end of a pressure hose 98 and 99 respectively which is connected at the other end to an air abrasive supply facilities such as S.S. White Companys model 11 (not shown) which moves abrasive particles under pressure through the hoses 98 and 99 and out of the nozzles 91 and 92 respectively.

As can be appreciated, the amount of material re- 27 microns; moving the particles under a pressure of psi through a nozzle opening having a diameter of 0.026 inches; positioning the nozzle opening onefourth inch away from the surface to be cleaned; and moving the surface to be cleaned past the air abrasive particles at a rate of 60 inches per minute. Thicker films can be removed from a surface by either increasing the size of the air abrasive particles, or increasing the pressure under which they are moved, or decreas ing the distance between the nozzle and the surface to be cleaned, or decreasing the rate of movement of the surface to be cleaned past the air abrasive particles.

Orientation of the substrate 11 (FIG. 1) to present the surface 12 having the resistor track 13 formed therein to the surface of the tires 81 and 82 will now be considered. The instance where a substrate has a rectangular shape, which is the normal shape of the substrate used in Thin Film Resistor manufacture, with a resistor track embossed on the widest side (see FIG. 1), the rectangular shape of the substrate may be used to orient the substrate prior to removing the resistor material 18 from the sides 1616 of the substrate 11 (see FIG. 1).

For example a conventional orienting device such as a vibratory feeder (not shown) is connected to one side of a rectangular tube 181 which passes through a hole 102 formed in the top plate 31 and is connected to a feeder 183 which has a rectangular track 108 (see FIG. 3) formed therein to form a continuous rectangular path. Referring now to FIG. 3, the feeder 103 is positioned between the wheels such that the widest side of the track 188 formed therein is next to the periphery of the tires 81 and 82 and close enough to the top of the contact area formed by the tires 81 and 82 so that one end of the substrate is in the track 104 while the other end is engaged by the tires 81 and 82.

Referring now to FIG. 2'and 3, the orienting device (not shown) moves only those substrates which are properly oriented with respect to the rectangular tube 101 into the tube 101. The substrates move through the tube 181 and feeder 183 under the force of gravity and sequentially drop onto the contact area of the tires 81 and 82. In this manner, the surface 12 having the resistor track 13 embossed therein will always be engaged by one of the tires 81 and 82. Although discussion was directed to a rectangular shaped substrate, it is to be understood that any shape substrate can be cleaned.

As mentioned previously, the substrates individually emerge from the feeder 183 under the force of gravity and drop on the contact area of the tires 81 and 82. As the wheels 78 and 79 rotate in opposite directions a substrate is engaged by the tires 81 and 82 and the substrate is pulled therebetween. The substrate 11 as it is moved between the tires 81 and 82 moves the wheel 78 and the shaft 66 to the right against the action of the spring 62 which urges the boss 87 to pivot about the drive shaft 81 to the left as viewed in FIG. 2. In this manner, the wheel 78 is continually urged toward the wheel 79 to move the resilient material of the tires 81 and 82 against the surface 12 and the opposite surface to mask the surfaces and to displace the substrate 11 relative to the air abrasive particles eminating from the nozzle 91 and 92.

As the substrate 1 1 is further displaced relative to the stream of air abrasive particles, the air abrasive particles remove the unwanted resistor material 18 from the sides 16-16 of the substrate 11 (see FIG. 1). Further displacement of the substrate 11 relative to the stream of air abrasive particles, moves the substrate 11 from contact with the surface of tires 81 and 82 and drops into a wire basket 105 positioned beneath the wheels 78 and 79 while the end of the next substrate is engaged by the tires 81 and 82 to repeat the cycle.

If a closed cleaning chamber 27 is used the air abrasive material may be removed by providing a hole 106 in the base 22 and connecting one end of a vacuum hose 107 thereto. Vacuum equipment (not shown) is connected to the other end of the hose 107 to pull out the abrasive material from the cleaning chamber 27.

OPERATION A vibrating feeder (not shown) is loaded with a plurality of substrates 11 (see FIG. 1) after removal from an evaporating or sputtering chamber (not shown). The vibratory feeder (not shown) moves substrates 11 one at a time into a rectangular shaped tube 101. The substrates 11 move under the force of gravity through the tube 101 into a rectangular track 104 formed in a feeder 103 and drop between urethane tires 81 and 82 to present surface 12 of the substrate 11 and the surface opposite thereto to the tires8l and 82. A motor 46 rotates a drive shaft 41 which rotates a gear wheel 42 mounted thereon. Rotation of the gear wheel 42 in a clockwise direction simultaneously rotates gear wheel 68 to rotate the wheel 78 through shaft 66 in a counterclockwise direction which rotates gear wheel 74 in a clockwise direction through shaft 71 as viewed in FIG. 2. A boss member 47 pivotally mounted on the shaft 41 maintains the shaft 66 to the left as viewed in FIG. 1 under the biased action of spring 62.

The leading end.of the substrate 11 is frictionally engaged to move the surface 12 and the surface opposite thereto between the tires 81 and 82. As the substrate 11 is moved therebetween the wheel 78 is moved to the right against the biased action of the spring 62 to accommodate the center portion of the substrate 11 which is thicker than the ends between the wheels 78 and 79 and maintain positive engagement of the substrate 11 as the spring 62 biases the boss member 47 to the left about the dirve shaft 41 and the wheel 78 as viewed in FIG. 2. Biasing of the wheel 78 toward the wheel 79 causes the urethane tires 81 and 82, respectively, to yield to the surface 12 and the surface opposite thereto thereby masking the surface 12 and the opposite surface.

Further displacement of the substrate 11 by the rotation of the wheel 78 and 79 moves the sides 16-16 of the substrate 11 past a stream of abrasive particles eminating from a pair of nozzles 91 and 92 each of which are positioned on sides of wheels 78 and 79. The unwanted material 14 is being removed, the wheels 78 and 79 continually move the substrate 11 by way of the tires 81 and 82, respectively, relative to the air abrasive particles while masking the surface 12 and the surface opposite thereto. Continued rotation of the wheels 78 and 79 further displaces the substrate 11 to move the next substrate between the tires 81 and 82. When the ends of the substrate are engaged by the tires 81 and 82, the wheel 78 is moved to the left as viewed in FIG. 2 under the biasing action of the spring 62 which pivots the boss member 47 about the shaft 41 to move the shaft 66 to the left as viewed in'FlG. 2. Further rotation of the wheels 78 and 79 moves the substrate 11 from between the tires 81 and 82, respectively, and the substrate 11 drops into a basket positioned between the wheels 78 and 79 while the next substrate is displaced relative to the abrasive from the air abrasive nozzles 91 and 92 to repeat the cycle.

As can be appreciated the apparatus described allows removal of unwanted material from opposite sides of a substrate without mechanically damaging the substrate. Further the apparatus is inexpensive to construct, does not require precision set up and continual maintainance to operate.

What is claimed is:

1. An apparatus for removing material from a selected side of an article without removing material from two sides of the article directly adjacent the selected side, comprising:

a nozzle;

means for forcing abrasive particles under air pressure through the nozzle;

means for displacing the selected side of the article relative to the nozzle and for masking the two sides of the article directly adjacent the selected side to protect the adjacent sides of the article from the abrasive particles.

2. An apparatus for removing material from selected sides of an article without removing material from two sides directly adjacent each of the selected sides, comprising:

a nozzle;

means for forcing abrasive particles under air pressure through the nozzle;

a pair of circular disks for engaging the two sides of the article directly adjacent each of the selected sides to mask the adjacent sides of the article from the abrasive particles, at least one of said disks being biased towards the other disk; and

means for rotating the disk to advance the article therebetween while masking the adjacent sides of the article.

3. The apparatus as set forth in claim 2 wherein said engaging means includes a tire of resilient material mounted on each of said disks.

0 i t t 

1. An apparatus for removing material from a selected side of an article without removing material from two sides of the article directly adjacent the selected side, comprising: a nozzle; means for forcing abrasive particles under air pressure through the nozzle; means for displacing the selected side of the article relative to the nozzle and for masking the two sides of the article directly adjacent the selected side to protect the adjacent sides of the article from the abrasive particles.
 2. An apparatus for removing material from selected sides of an article without removing material from two sides directly adjacent each of the selected sides, comprising: a nozzle; means for forcing abrasive particles under air pressure through the nozzle; a pair of circular disks for engaging the two sides of the article directly adjacent each of the selected sides to mask the adjacent sides of the article from the abrasive particles, at least one of said disks being biased towards the other disk; and means for rotating the disk to advance the article therebetween while masking the adjacent sides of the article.
 3. The apparatus as set forth in claim 2 wherein said engaging means includes a tire of resilient material mounted on each of said disks. 